Kernel dumps [was Re: possible changes from Panzura]

[asomers at gmail.com]

On Wed, Jul 10, 2013 at 12:57 PM, Jordan Hubbard <jkh at mail.turbofuzz.com> wrote:
>
> On Jul 10, 2013, at 11:16 AM, Julian Elischer <julian at elischer.org> wrote:
>
>> My first  candidates are:
>
> Those sound useful.   Just out of curiosity, however, since we're on the topic of kernel dumps:  Has anyone even looked into the notion of an emergency fall-back network stack to enable remote kernel panic (or system hang) debugging, the way OS X lets you do?  I can't tell you the number of times I've NMI'd a Mac and connected to it remotely in a scenario where everything was totally wedged and just a couple of minutes in kgdb (or now lldb) quickly showed that everything was waiting on a specific lock and the problem became manifestly clear.
>
> The feature also lets you scrape a panic'd machine with automation, running some kgdb scripts against it to glean useful information for later analysis vs having to have someone schlep the dump image manually to triage.  It's going to be damn hard to live without this now, and if someone else isn't working on it, that's good to know too!

I don't doubt that it would be useful to have an emergency network
stack.  But have you ever looked into debugging over firewire?  We've
had success with it.  All of our development machines are connected to
a single firewire bus.  When one panics, we can remotely debug it with
both kdb and ddb.  It's not ethernet , but it's still much faster than
a serial port.
https://wiki.freebsd.org/DebugWithDcons

>
> - Jordan
>
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